1. Field of the Invention
The present invention relates to the locking mechanism in door locks of the type which allow the handle to xe2x80x9cfree-wheelxe2x80x9d, i.e., rotate without retracting the latch bolt, when the mechanism is locked.
2. Description of Related Art
Doors are much easier to open when the door handle is shaped as a lever handle rather than a conventional door knob. For this reason, lever handles are preferred in some applications, and they may be required under applicable regulations for certain doors in public buildings to facilitate access by the disabled and the elderly.
However, the lever shape of the door handle allows much greater force to be applied to the internal locking mechanism of the door than can be applied with a round door knob. In most door locks, the locking mechanism prevents the door knob from turning when the door is locked. When a round door knob is replaced by a lever handle, the greater leverage available from such a handle may allow a vandal or thief to break the internal components of the door lock by standing or jumping on the lever end of the handle. This problem is particularly acute for cylindrical locks which have less internal room than mortise type locks to accommodate heavy duty locking components.
To address this problem, the present invention has been designed such that the outer lever handle is disengaged from the locking mechanism and allowed to free-wheel when the door lock mechanism is locked. This allows the lever handle to rotate freely without operating the locking mechanism and prevents the lever handle from being used to overstress the internal components of the lock.
Free-wheeling door locks which have previously been developed have been expensive due to the large number of parts, the multiple manufacturing steps needed to make the parts and the difficulty of assembly of the lock at the factory. U.S. Pat. No. 4,920,773 is indicative of such a free-wheeling lock wherein numerous components are necessary to disengage the lever handle from the lock. In particular, such components are necessary when the spindle is to be disconnected from the lever handle.
In prior art designs, the spindle has heretofore always been directly and non-rotatably connected to the handle operating it. The present invention addresses these problems through a design which includes relatively fewer parts and simpler parts that can be manufactured with fewer steps and which are quickly and easily assembled in the factory and in the field. The present invention also addresses this problem by designing the spindle so that it may continue to be directly and non-rotatably connected to the spindle as in the prior art designs, while still providing free-wheeling operation when locked.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a free-wheeling lever handle lock mechanism that is relatively less expensive to construct and assemble than prior art free-wheeling lock mechanisms.
It is another object of the present invention to provide a free-wheeling lever handle lock mechanism that has fewer components than prior art free-wheeling lock mechanisms, and where the components are easy to manufacture and assemble.
A further object of the present invention is to provide a free-wheeling lever handle lock mechanism wherein the lever handle always turns the spindle to which it is attached.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects, which will be apparent to those skilled in art, are achieved in the present invention which is directed to a free-wheeling lock mechanism which includes a latch retractor, a spindle having an inwardly projecting finger, and a cam rotatably held within the spindle. The cam includes a cam scoop that retracts the latch retractor when the cam is rotated and a cam slot which interacts with the finger on the spindle to lock and unlock the mechanism.
The cam slot has a longitudinal portion and a circumferential portion and the cam is axially slidable relative to the spindle from an unlocked position to a locked position. In the unlocked position the finger projects inwardly from the spindle into the longitudinal portion of the cam slot to couple the spindle to the cam. In this position rotation of the spindle rotates the cam to open the door. In the locked position the finger projects inwardly from the spindle into the circumferential portion of the cam slot. In this position the spindle will free-wheel relative to the cam and rotation of the spindle will not open the door. This design allows the lever handle to be directly and non-rotatably connected to the spindle in the usual manner of lock mechanism that do not free-wheel, while still providing free-wheeling performance. This arrangement provides for a lower cost device.
In the described embodiment of the invention the cam is biased by a cam spring to slide axially relative to the spindle and position the finger in the longitudinal portion of the cam slot. A lock cylinder assembly is provided which may be turned by a key to turn a tail extending from the lock cylinder. The cam includes an opening for receiving the lock cylinder tail and rotation of the lock cylinder will rotate the cam with the lock cylinder tail to retract the retractor and open the door when the mechanism is locked.
In the preferred embodiment, the cam includes a key guide which is non-rotatably held in an end of the cam opposite the cam scoop and which includes an opening for receiving the lock cylinder tail. The key guide is held in the cam by a lock piece and the lock piece engages the key guide, extending through the key guide and through the cam perpendicular to the central axis of the cam. A cam spring is located between the spindle and the key guide to urge the cam towards the unlocked position.
The lock mechanism also includes a second spindle adapted for non-rotatable connection to a second handle to be mounted on the inner side of the door. The second spindle is located on an opposite side of the latch retractor from the first spindle and has a button lock mechanism mounted within it. The button lock mechanism includes an actuator that extends through the lock and contacts the cam. The actuator is axially movable to move the cam between the locked and unlocked positions.
In the most highly preferred embodiment of the free-wheeling lock mechanism the button lock mechanism is rotatable between first and second positions. In the first position the button lock mechanism allows the cam to return to the unlocked position whenever the latch retractor is retracted. In the second position the button lock mechanism continuously holds the cam in the locked position even after the latch retractor is retracted. Thus, in the first position opening the locked door with the key or the inner handle will unlock the door, while in the second position, opening the door by either method will not leave it unlocked.
The outer lever handle is preferably directly attached in a non-rotatable manner to the spindle via a hollow shaft portion which receives and engages the spindle and the lever portion of the handle is supported in a horizontal orientation by a spring mounted in the rose surrounding the hollow shaft portion of the lever handle.